This invention pertains generally to a circuit arrangement for actuating a warning device in response to predetermined conditions of a vehicle brake system.
In vehicles equipped with hydraulically actuated power brake boosters, an engine-driven or main source of hydraulic pressure, such as a power steering pump, may be utilized in combination with a back-up source of hydraulic pressure, such as a second pump driven by an electric motor powered off the vehicle battery. This type of braking system is disclosed in co-pending application Ser. Nos. 83,440 and 83,441, which are commonly assigned with the present application.
When the vehicle and brake system are operating normally, the power steering pump operates when the vehicle engine is operating. Therefore, an abnormal condition exists when the ignition switch is "on", but the main power steering pump is not operating.
The system illustrates an electronic brake system warning circuit generates a warning signal in response to various conditions of such a brake system. However, this warning circuit does not generate a warning signal in response to the above-mentioned abnormal condition, unless simultaneously with this condition, there also occurs either (1) an operator brake application, or (2) an open circuit condition in the auxiliary pump motor.